The incidence of cerebral attack, or stroke, suffered by CPM state secretary Anil Biswas on Saturday, is rising alarmingly in the city, prompting Bangur Institute of Neurology to undertake a study on the ailment.

Funded by the Indian Council of Medical Research, the study will cover around a lakh residents across Calcutta over a period of three years. The data collected will be analysed and put together in a report, which will be one of its kind in eastern India.

Bangalore is the other city where such a survey will be conducted.

'In our earlier survey on common neurological ailments, we had observed that incidence of stroke among urban people was on the rise. The study also revealed that residents of urban areas are thrice more susceptible to stroke than their rural counterparts. The finding has prompted us to conduct an in-depth study on cerebral attacks,' said institute director Trishit Roy, who is also on the board in charge of the CPM leader's treatment.

The Longitudinal Study on Stroke in the City of Calcutta, as the study has been called, will zero in on the two basic types of strokes ' haemorrhagic and ischaemic. It will focus on five aspects ' including the number of new cases, fatality rate and the effect on human mobility and the brain.

The city will be divided into zones, each to be assigned to a team comprising doctors, field workers and neuro-psychologists.

'Apart from the epidemiological aspect, there are two important features of this study,' elaborated Shyamal Kumar Das, principal investigator of the project.

'First, we will be try to find out how patients in a pre-hypertension stage could become susceptible to stroke due to an increase in blood pressure caused by the change in lifestyle and related stress. Next, we will try to find out how the two types of stroke are affecting people who have crossed 60 years,' he added.

Experts say that of the two types to be covered by the study, haemorrhagic stroke, which has affected Biswas, is more dangerous, as it hardly gives any warning.

The study will ascertain how many of the haemorrhagic stroke patients were having uncontrolled hypertension or an abnormality in the blood vessel (aneurysm) or a congenital defect in the blood vessels caused by a lack of the protective covering (arterio-venus malformation).

As for ischaemic strokes, the study will find out how many patients were diabetic and how many have suffered a stroke due to smoking.